A comparison of detection methods for foliar nematodes in herbaceous ornamental crops

The source of foliar nematode (Aphelenchoides spp.) problems in ornamental crops is often traced to infested cuttings, liners, or rootstocks. Early detection of foliar nematodes can be problematic because infested plants may not initially show symptoms. As a result, infested material is often unknowingly propagated or shipped to other locations. A traditional water extraction method was compared to an A. fragariae specific, PCR-based diagnostic assay to detect the presence of foliar nematodes in blocks of plants grown in a commercial greenhouse. A block of 44 ferns, and a second block of 73 anenome plants were sampled. Six 6 mm leaf disks were removed from each plant. Water extraction was used to assay one half of the leaf disks and the remaining three disks were assayed by PCR. Three ferns tested positive for foliar nematodes by both detection methods, with an additional 24 ferns testing positive only by the PCR method. The remaining 17 ferns were negative by both methods. Three of the anemone plants were positive by both methods, while 48 of the plants tested positive only by PCR. The remaining 22 anenomes were negative by both methods. The traditional water extraction method failed to detect nematodes in 55% and 66% of the fern and anenome samples, respectively. Accurate and early detection by PCR will help growers maintain nematode-free stock plants and facilities.